Older Hydrothermal Alteration in the Yellowstone Caldera

智力上的优点。怀俄明州黄石国家公园的黄石河大峡谷暴露出垂直300-400米的热液蚀变火山岩，这些火山岩鲜为人知。沿着峡谷的露出地面的岩层包含了较老的（化石）黄石热液系统的最高部分。公园内没有其他地方可以进入热液系统的横截面，峡谷有可能了解其他地方无法进入的更深的系统。黄石公园的活跃温泉是众所周知的，作为蒸汽主导系统的表面表达，提供了一个模型，可以对这里提出的研究结果进行测试。初步的实地和实验室工作发现，在峡谷壁酸性硫酸盐和碱性氯化物低温热液矿物组合。这些数据表明，在过去的某个时间存在两种流体，类似于今天在活动系统中发现的两种流体。这里提出的研究将奋进于提供一个基于流体沸腾上升沿着流体静力沸腾曲线的300-400米的老热液系统的重建，将评估黄石热液系统的寿命，将检查老流体及其关系，并将评估黄石公园系统中随时间推移通过上地壳的热液质量和能量通量。黄石公园每年有来自世界各地的数百万人参观。他们带着对公园地质奇观的极大兴趣和好奇心而来。黄石河的大峡谷是公园中最受欢迎的景点之一，但关于峡谷的变化的科学信息很少。事实上，这一变化是公园名称的来源。希望这里提出的研究结果将提供给公园的游客，以提高他们对塑造公园的地质过程的理解和欣赏，以及他们周围的世界。其他更广泛的影响包括火山灾害、地热资源和成矿过程的应用。

Intellectual merit. The Grand Canyon of the Yellowstone River, Yellowstone National Park, Wyoming, exposes 300-400 vertical meters of hydrothermally altered volcanic rocks that are very poorly known. The outcrops along the canyon contain the uppermost parts of the older (fossil) Yellowstone hydrothermal system. No other locations in the park provide access to cross-sections of the hydrothermal system, and the potential exists in the Canyon to learn about the deeper system that is elsewhere inaccessible. The active thermal springs at Yellowstone are well known, and as the surface expression of the vapor-dominated system, provide a model against which the results of the research proposed here can be tested. Preliminary field and laboratory work has found both acid-sulfate and alkali chloride epithermal mineral assemblages in the Canyon walls. These data suggest the presence of two fluids at some time in the past, analogous to the two fluids found in the active system today. The research proposed here will endeavor to provide a reconstruction of the upper 300-400 meters of the older hydrothermal system based on boiling in a fluid rising along the hydrostatic boiling curve, will evaluate the longevity ofthe Yellowstone hydrothermal system, will examine the older fluids and their relationships, and will assess hydrothermal mass and energy flux through the upper crust over time in the Yellowstone system.Broader Impacts. Yellowstone Park is visited by millions of people from around the world every year. They come with a great interest in and curiosity about the park's geologic wonders. The Grand Canyon of the Yellowstone River is one of the most popular sites in the park, yet very little scientific information about the alteration in the canyon is available. This alteration, in fact, is the source of the park's name. It is hoped that the results of the research proposed here will be made available to the park's visitors to enhance their understanding and appreciation of the geologic processes that have shaped the park, and the world around them. Additional broader impacts include applications to volcanic hazards, geothermal resources, and ore-forming processes.